There are a number of spotters at CHC that could help try contacting them by email.

There is an outdoor observation deck on top of the terminal which is sometimes closed if ice is on it. International is at one end of the terminal and domestic at the other. Mornings are good for shooting from the terminal and near the fire station along the road. You will need transport and it is possible to go right around the airport using the roads if you have a car. The afternoons are best shot from the Canterbury Aero Club side which is directly opposite the tower on the other side of the runways. Aero Club is quite active and uses the grass parrallel runways most of the time. They have been getting a bit of snow in the south island in the last few days.

Might be a good idea to email some of the spotters that are there for more info?
As you are there for 3 months keep an eye on the Air NZ grabaseat web site as they have daily specials to other places at very reasonable prices.

Hi PrattWhitney, , you have chosen the right time to come down to CHC, it is coming into summer down here, so the weather should be quite good.
Also as you know Xmas is just around the corner!
bigjuliechc